Archive for January, 2013

Soft UART on LPC13xx

23. January 2013 11:32 by Jens Willy Johannsen
Categories: ARM | Projects

For the ROV project I need two UART connections (one for RS485 to the onboard controller and one for receiving input from the VNC2 USB host controller).

And since the LPC1347 only has one UART I needed a soft UART for one of the connections. Fortunately for me, NXP provides an implementation in AN10955. There was only one problem with it: it doesn't work. Or rather, it works for a while and then stops receiving anything (scoping the UART line confirmed that the VNC2 chip continued to send data so the problem had to be in the soft UART code).

Yea, intermittent errors – what's not to like… (Read on for the problem and the solution.)

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New power supply

20. January 2013 12:50 by Jens Willy Johannsen
Categories: General

How, oh how did I ever live without it?
Just before Christmas I finally caved in (to myself) and got myself a decent bench-top power supply. A TTi PL303-QMD (datasheet/brochure here).

Yes sure, there are more advanced units out there but this one suits my needs just fine: dual 3 ampere outputs (which can be paralleled together for a total of 6 amps), voltage span setting (so the voltage dial only adjusts voltage from e.g. 3.0 to 3.4), 500 mA mode (allowing much finer control over the current setting up to 500 mA).

And now I can't imagine how I ever got by without it. So if you are considering splurging on a decent PSU, consider no more and get this one right now!

PL303QMD (click for larger image)

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